The present disclosure relates to a vehicle driving assistance apparatus that scans light emitted from a coherent light source such as a semiconductor laser, to draw a predetermined light pattern on a road surface around an own vehicle, and enables a driver of the own vehicle, drivers of other vehicles, pedestrians, and an environmental condition detector to recognize the drawn light pattern, thereby contributing road safety.
As an existing technology that displays any light pattern on a road surface around an own vehicle with use of a laser beam such as a semiconductor laser and enables a driver of the own vehicle, drivers of other vehicles, pedestrians, and an environmental condition detector to recognize the displayed light pattern, for example, a technology disclosed in Japanese Unexamined Patent Application Publication No. H05-238307 (JP-H05-238307A) is exemplified. The technology disclosed in JP-H05-238307A projects a visible spot marker or a diagram such as a polygon through scanning with use of a two-dimensional galvanometer, on a front position distanced by a predetermined length from the vehicle on a road surface. This makes it possible to enable pedestrians and drivers of other vehicles to recognize presence of the own vehicle.
Further, in Japanese Unexamined Patent Application Publication No. 2003-231450 (JP2003-231450A), disclosed is a technology in which an image pickup apparatus acquires a light pattern formed on a road surface by a laser beam that is emitted by the own vehicle and other vehicles and a condition to be noted in traveling of the own vehicle is determined based on information of the light pattern. In this technology, a traveling track where the own vehicle is supposed to travel is calculated based on a vehicle speed, a motion state quantity, a steering angle, and steering force of the own vehicle. Right and left boundaries between a zone where the vehicle passes and a zone where the vehicle does not pass in a case where the own vehicle is assumed to travel on the calculated traveling track are calculated, and a scan actuator scans a laser beam to draw a part of the boundaries necessary for safety depending on the speed and other factors.
Further, in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2004-526612 (JP2004-526612A), disclosed is a technology of displaying a light pattern on a road surface behind the own vehicle with use of a method used in a field of illumination effect for a spectacular show, and providing a following vehicle with information when an accident occurs or the own vehicle is urgently stopped.
These technologies just mentioned above are based on the assumption that the laser beam forming the light pattern projected on the road surface is irregularly reflected by the road surface and is diffused substantially uniformly in all directions less depending on an entering direction of the light. When the road surface is wet in the rain, however, in particular, in a case of a light beam entering the road surface at a shallow angle (i.e., an angle formed by the light beam with the road surface is small), such assumption is not established and a regularly reflected component dominates. Thus, if the regularly reflected component of the laser beam that forms the light pattern projected on the road surface directly enters eyes of a driver of an oncoming vehicle accidentally, the driver is strongly dazzled, which may cause occurrence of a traffic accident.
To address such a disadvantage of dazzlement, for example, Japanese Unexamined Patent Application Publication No. 2003-231438 (JP2003-231438A) discloses a technology of applying, with consideration for a wet road surface, a visible beam while avoiding a pedestrian when the pedestrian as an obstacle is detected based on contrast of an image of the road surface irradiated with the laser beam that forms the light pattern projected on the road surface. The image of the road surface is picked-up by an image pickup apparatus.
Further, Japanese Unexamined Patent Application Publication No. 2003-285685 (JP2003-285685A) discloses a technology in which a glass plate that forms a Brewster angle with respect to a beam from a semiconductor laser is interposed with consideration for the wet road surface. JP2003-285685A teaches that, in doing so, a polarized component parallel to the road surface is reflected by the glass plate and removed, which may prevent the laser beam forming the light pattern projected on the road surface from being regularly reflected strongly even by the wet road surface, and thus may resolve the disadvantage of dazzlement to the pedestrians and drivers of other vehicles.
Further, Japanese Unexamined Patent Application Publication No. 2011-157022 (JP2011-157022A) discloses a vehicle head lamp that makes it possible to dynamically generate a desired light distribution pattern through scanning the beam from the semiconductor laser while modulating intensity of the beam. The light of the vehicle head lamp is dimmed or is turned off in a region closer to the vehicle than a region where a light distribution pattern of a normal low beam is applied, as a light distribution pattern for rainy weather.